The invention concerns a compression tool, in particular for joining tubular workpieces, with more than two arcuate compression jaws so movable relative to each other that they can open in order to be placed on the workpiece and that they complement one another into a closed compression space toward the end of compression, and also comprising at least one drive system to move the compression jaws towards the workpiece for compression therebetween.
Metal coupling sleeves, preferably steel, and plastically deforming, are employed to join pipe ends. The sleeve inside diameter exceeds the outside diameter of the pipe ends to be joined by an amount such that when being radially compressed, they remain deformed until coming to rest against the outside of the pipe ends. As disclosed by the German Patent No. 1,187,870, such coupling sleeves additionally may comprise an annular groove near each end which receives an elastic sealing ring.
Radial compression may be implemented by compression tools, such as illustratively known from the German Patent No. 21 36 782. This compression tool comprises two clamping jaws, each with two arms and at least one clamping jaw being pivotably supported on the compression tool. The compression jaws comprise compression surfaces forming arcs of circle of equal radii, enclosing a compression space. Instead of being arcs of circle, the compression surfaces also may be contoured, for instance to form a polygonal or oval compression space.
The arms of the compression jaws away from the compression space can be spread apart against the force of a spring, whereby the compression jaws move relative to each other in the region of the compression space. The spreading apart takes place by means of adjacent and abutting pressure rollers which are jointly moved by a drive system comprising an operational cylinder between the arms for thereby causing pivoting of the compression jaws.
The German Offenlegungsschrift 34 33 283 describes a compression tool of this type. In that compression tool, there are two compression jaws each pivotably supported on a drive lever which is in turn pivotably guided on the compression tool. The drive levers comprise opposite arms which can be spread apart by pressure rollers moved by an operational cylinder into the gap between the arms. Moreover, the compression jaws are guided in slide means so that, upon the drive levers being pivoted into the open position, they will be pivoted up about their linkages at the drive whereby a wide, tong-like aperture is created between the compression jaws, facilitating the seating of the pipe ends to be joined, or of a coupling sleeve.
When pivoting the drive levers in the reverse direction, the clamping jaws again are so pivoted so that the mid-perpendiculars to their arcs of circle approximately coincide, and upon further pivoting motion of the drive levers the clamping jaws are displaced relative to one another in parallel manner. The clamping jaws are further displaced during compression until at the end of this compression they enclose a circular surface, whereby they have deformed the pipe ends or the coupling sleeve by a corresponding reduction in diameter.
This compression tool has been found practically useful, provided that a comparatively modest reduction in diameter or squeeze depth is required. Where the squeeze depths are more substantial--which shall be the case when the pipe connection must withstand higher internal pressures, more than two compression jaws must be provided to prevent beads from being formed between the end faces of the compression jaws, or else complete closure will not take place. Such compression tools are known for instance from the German Offenlegungsschriften 21 28 782; 35 13 129; and the German Auslegeschriften 25 11 942 and 19 07 956. All the compression tools described therein share in common the feature that all the clamping jaws are displaceable and are guided in the radial direction. This entails complex guide means and drive systems, with the result that the compression tools become heavy and hard to handle, and also expensive.